1. Field of the Invention
The present invention relates to a device for sealing a liquid crystal injection hole of a liquid crystal cell when liquid crystal injection has been completed.
Liquid crystal panels are frequently used as simple display devices and are a strong candidate to be implemented as display devices, replacing CRTs (Cathode Ray Tubes). A conventional method to manufacture such a liquid crystal panel is disclosed, for example in document 1 (xe2x80x9cLatest liquid crystal technologyxe2x80x9d, Institute for Industrial Research (Sep. 1, 1984), pp. 156-167). FIGS. 12(A)-12(D) are drawings depicting this method. FIGS. 12(A)-12(D) in particular, show the liquid crystal injection step and the step of sealing a liquid crystal injection hole.
In this method, a first substrate 11 and a second substrate 13 for a liquid crystal panel where electrodes, elements for driving liquid crystals, and an orientation film (all not illustrated), are bonded with a sealing material 19, maintaining a predetermined gap 15 between the substrates (generally, the gap 15 is created by spacers 17). In this way, a crystal cell 21 (liquid crystal is not yet injected) is created (FIG. 12(A)). In a part of the crystal cell 21, a crystal injection hole 21a is created by, for example, creating a part that the sealing material does not coat in the sealing material coating step.
Then, inside the gap 15 of the crystal liquid cell 21 and liquid crystal 23, which is prepared to be injected into the gap, are degassed by exhaust means 25 (FIG. 12(A)). In FIG. 12(A), 23a is a tank for storing the liquid crystal 23, and 27 is a processing chamber to inject the liquid crystal 23 into the gap 15 of the liquid crystal cell 21. Then, this liquid crystal cell 21 is moved so that the liquid crystal injection hole 21a contacts the liquid crystal 23 (FIG. 12(B)). The processing chamber 27 is exhausted which ends at an appropriate time. When the liquid crystal injection hole 21a contacts the liquid crystal 23, the liquid crystal 23 is injected, to a degree, into the gap 15 by a capillary phenomenon (FIG. 12(B)).
Then, sufficiently dried inactive gas, such as argon or nitrogen, is supplied into the processing chamber 27 from gas supply means 29, and the liquid crystal fills the gap 15 of the liquid crystal cell 21 due to the pressure of the inactive gas (FIG. 12(C)).
Then, the liquid crystal injection hole 21a is closed (sealed) with an appropriate sealing material 19a (FIG. 12(D)). In this way, the injection of the liquid crystal and the sealing of the liquid crystal injection hole are completed.
To increase the productivity of liquid crystal panels, it is preferable to execute each process required for manufacturing liquid crystal panels in units of a large number of liquid crystal cells (in lot units). This is also true for the process to seal the liquid crystal injection hole of a liquid crystal cell after the completion of liquid crystal injection. In other words, it is better to seal the liquid crystal injection holes 21a in units of a large number of liquid crystal cells. This is because the processing time can be dramatically decreased as compared with a case of supplying the sealing material to the sealing areas of liquid crystal cells one by one (see the later mentioned FIG. 2(A)).
To execute the sealing operation in units of a large number of liquid crystal cells, it is preferable to supply the sealing material to the sealing areas of those liquid crystal cells simultaneously. Otherwise, if the sealing material is supplied to the sealing areas of a multiplicity of liquid crystal cells one by one, which takes time, the difference in time causes problems. For example, in some liquid crystal cells of the multiplicity of liquid crystal cells, the sealing material reaches the liquid crystal in the liquid crystal cells. In this case, a problem such as display quality deterioration occurs.
A possible device to supply the sealing material to the sealing areas of individual liquid crystal cells simultaneously is a device where a same number of dispensers (device to sequentially supply a predetermined quantity of viscous material utilizing gas pressure, a typical example is a syringe) as a number of sealing areas are arranged matching the arrangement of the multiplicity of liquid crystal cells, so that the sealing material can be simultaneously supplied to the sealing areas of individual liquid crystal cells using these dispensers.
In this case, however, there are problems such as the device becoming relatively large in scale, and the maintenance of the dispensers being troublesome.
With the foregoing in view, a liquid crystal sealing device with a new configuration which simultaneously supplies the sealing material to the sealing areas to seal the liquid crystal injection holes of multiplicity of liquid crystal cells respectively is desired.
Therefore, according to a first aspect of the present invention, there is provided a liquid crystal sealing device comprising a sealing material supply part for supplying sealing material simultaneously to a sealing area for sealing a liquid crystal injection hole of each one of multiplicity of liquid crystal cells when liquid crystal injection has been completed. The above mentioned sealing material supply part comprises: a multiplicity of pins which are arranged to match the arrangement of the sealing areas of the multiplicity of crystal cells, and are used for transferring the sealing material from a container storing the above sealing material to each sealing area, and a reciprocating mechanism for reciprocating these multiplicity of pins as one unit between a position where the above mentioned sealing areas are to be positioned and the above mentioned container.
According to this liquid crystal sealing device, the sealing material can be simultaneously transferred to the respective sealing areas of the multiplicity of liquid crystal cells by the pin transfer system using a multiplicity of pins. Also, the transfer pins are used so that the device can be simplified and maintenance management can also be simplified compared with, for example, the dispenser system.
The following configuration is preferable to embody the present invention. That is, a substrate pressure adjustment mechanism for adjusting pressure to press the two substrates of the above mentioned liquid crystal cell in the above mentioned sealing material supply part so that the phenomenon where the above sealing material is drawn into the above mentioned liquid crystal injection hole occurs in the liquid crystal injection hole when the above mentioned sealing material is contacted to the above mentioned sealing area by the above mentioned pin. For the above mentioned reciprocating mechanism, it is preferable to use a mechanism which contacts the above mentioned sealing material to the above mentioned sealing area by the pin during the time when the required quantity of the above mentioned sealing material is drawn into the above mentioned liquid crystal injection hole by the above mentioned drawing phenomenon, and then releases the pins from the sealing area.
According to this preferred example, the sealing material is drawn into the liquid crystal injection hole, so that the liquid crystal injection hole can be sealed with the necessary minimum amount of sealing material. In other words, there is another effect of preventing the phenomenon where the liquid crystal material builds up and attaches to the side face of the liquid crystal injection hole side of the liquid crystal cell (e.g. the phenomenon shown in FIG. 12(D)). If the sealing material builds up on the side face of the liquid crystal cell, the outside dimension of the liquid crystal cell increases. Such an outside dimensional deviation should be prevented, since recently high-density packaging is required. According to this preferred example, the above mentioned outside dimensional deviation can be prevented.
To embody the present invention, it is preferable to use a porous element which can be impregnated with the above mentioned sealing material and which has elasticity at the respective tips of the above mentioned pins. It is preferable to use a substrate pressure adjustment mechanism for adjusting the pressure to press the two substrates of the above mentioned liquid crystal cells, so that the phenomenon where the above mentioned sealing material is drawn into the above mentioned liquid crystal injection hole occurs at the liquid crystal injection hole when the porous element is contacted to the above mentioned sealing area. It is preferable that the above mentioned reciprocating mechanism contact the above mentioned porous element with the above mentioned sealing area during the time when the required quantity of the above mentioned sealing material is drawn from the above mentioned porous element into the above mentioned liquid crystal injection hole by the above mentioned drawing phenomenon.
According to this preferred example, only the sealing material drawn by the above mentioned drawing phenomenon is drawn from the porous element into the liquid crystal injection hole. Therefore, compared with the above mentioned preferred example, which simply uses the pins and the drawing phenomenon, the unnecessary attachment of sealing material on the side wall of the liquid crystal cell can be more completely prevented.
In the above description, examples where the porous elements are disposed at the tips of multiplicity of pins corresponding to the multiplicity of liquid crystal cells were described, but it is also possible not to use the pins.
In other words, according to a second aspect of the present invention, there is provided a liquid crystal sealing device, and as later described with reference to FIG. 11, wherein the porous elements are arranged to match the arrangement of the sealing areas of the multiplicity of liquid crystal cells. For example, a porous element which has a shape covering the sealing areas of the multiplicity of liquid crystal cells is used, or an appropriate support, a frame for example, which covers the sealing areas of the multiplicity of liquid crystal cells, is provided, and each porous element is disposed at the areas facing the sealing areas of the multiplicity of liquid crystals cells on this frame.
The concept of drawing the sealing material into the liquid crystal hole using the porous element, can certainly be applied to a case when a liquid crystal injection hole of one liquid crystal cell is sealed, and is not limited to the case when individual liquid crystal injection holes of the multiplicity of liquid crystal cells are sealed simultaneously.
In other words, according to a third aspect of the present invention, there is provided a liquid crystal sealing device comprising a sealing material supply part for supplying sealing material to a sealing area for sealing the liquid crystal injection hole of a liquid crystal cell where liquid crystal injection has been completed, wherein the above mentioned sealing material supply part further comprises: a porous element which can be impregnated with the above mentioned sealing material and which has elasticity; a substrate pressure adjustment mechanism for adjusting the pressure to press the two substrates of the above mentioned liquid crystal cell so that the phenomenon where the above mentioned sealing material in the porous element is drawn into the above mentioned liquid crystal injection hole occurs at the liquid crystal injection hole when the above mentioned porous element is contacted to the above mentioned sealing area; and a porous element moving mechanism which operates such that the above mentioned porous element is contacted to the above mentioned sealing area during the time when a required quantity of the above mentioned sealing material is drawn from the above mentioned porous element into the above mentioned liquid crystal injection hole by the above mentioned drawing phenomenon, and is then released. According to this, the sealing material is injected only into the liquid crystal injection hole, even when one liquid crystal cell is sealed, so that a liquid crystal cell with a high outside dimension accuracy can be manufactured.